1. Field of the Invention
The present invention generally relates to semiconductor devices and methods for producing the same, and more particularly to a semiconductor device and a method for producing the semiconductor device, which is configured to have a plurality of semiconductor elements stacked therein.
In recent years, with increasing demand for miniaturized portable equipment such as a portable telephone, a semiconductor device that is installed therein has also been required to have a smaller size. In order to support this situation, a stack-type semiconductor device, which has a plurality of semiconductor elements stacked within resin for encapsulation (a package) thereof, is developed.
2. Description of the Related Art
FIG. 1 shows a conventional stack-type semiconductor device 1, comprising a plurality of semiconductor elements 2, 3 (two in this diagram) which are carried by a stage portion 5a of a plurality of leads 5.
Specifically, the semiconductor element 2 is installed under the stage portion 5a and the semiconductor element 3 is installed on the stage portion 5a, each with adhesive 12 and in a face-up state. Accordingly, electrodes 7 provided on the semiconductor element 2 and electrodes 8 provided on the semiconductor element 3 face away from the stage portion 5a.
The electrodes 7 and 8 are connected to bonding pads 5c of the leads 5 by wires 10 and 11, respectively. Also, outer leads 5b of the leads 5 are formed extending out of encapsulating resin 6, for example, like a gull wing.
Thus, by installing the plurality of semiconductor elements within the encapsulating resin 6, the semiconductor device 1 can be produced with a smaller size and lighter weight, compared to a semiconductor device where the semiconductor elements are separately packaged.
In the semiconductor device 1 where the plurality of semiconductor elements are installed, however, in a case where a plurality of wires are simultaneously bonded to one bonding pad 5c to connect electrodes, electrical characteristics and signal characteristics of the electrodes need to be equal. That is, the electrodes to be connected by the wires should be equi-electrodes.
As shown in FIG. 1, if the semiconductor element 2 and the semiconductor element 3 are the same type semiconductor elements just different in size, then the electrodes 7 and 8 of the semiconductor elements 2 and 3 are the same in electrode layout. Accordingly, in a case where the semiconductor element 2 is directly stacked on the semiconductor element 3, two up-and-down adjacent electrodes 7 and 8 become equi-electrodes, and therefore can be connected by a wire running up and down.
In the conventional semiconductor device 1, however, the leads 5 (the stage portion 5a) are interposed between the semiconductor elements 2 and 3 as shown in FIG. 1. According to this configuration, the electrodes 7 of the semiconductor element 2 and the electrodes 8 of the semiconductor element 3 are symmetrical with respect to the stage portion 5a, respectively. That is, the electrodes 7 have a mirror relationship with the electrodes 8, respectively. But two electrodes 7 and 8 that have the mirror relationship are not equi-electrodes even if the semiconductor elements 2 and 3 are the same type semiconductor elements because those equi-electrodes 7 and 8 are separated in a diagonal, not an up-and-down, relationship. Therefore, in the conventional semiconductor device 1, the wire cannot be directly connected between the two up-and-down electrodes 7 and 8.
Accordingly, in a case of wiring those equi-electrodes 7 and 8 that are thus separated, the wires 10 and 11 need to be each laid with a large angle, and thereby a problem is brought about that the wiring becomes troublesome and easy to generate a short circuit due to contact of the wires.
In order to make the up-and-down electrodes 7 and 8 be equi-electrodes available connection, in a case where the semiconductor element 2 is different from the semiconductor element 3 in structure and the semiconductor element 2 is set as a standard, the semiconductor element 3 needs to be re-designed and re-produced so that the electrode layout thereof can have the mirror relationship with that of the semiconductor element 2. This brings about a cost increase in producing the semiconductor device 1.